The subject invention relates to optical punched card and badge readers. These devices typically hold fixed instructions or data, and are particularly useful in security systems, hospitals, parking lots, time-clocks and other data collection or process control systems.
As is well known, optical card readers transform the punched holes in data cards into electrical impulses. This is accomplished by passing the data card between an array of light sources and a corresponding array of light-sensors, typically photoelectric cells. Light from the light source will be detected by the photoelectric cells at locations on the data card where a punched hole exists, thereby generating an electric impulse. These generated signals then are carried by well known circuitry to a readout terminal or device.
U.S. Pat. No. 4,114,028 which issued to Alfred R. Baio on May 26, 1977, entitled "Optical Punched Card Reader" and which is assigned to the assignee of the subject application, discloses a device which utilizes the principles described above. It is seen in FIG. 1 of that patent that the apparatus includes a slot that is dimensioned to slidably accept the data card. FIGS. 4 and 5 of that patent further show that the apparatus includes a strobe generator which cooperates with the data card to slide within the slot toward and away from the opening in the apparatus. The electrical components of the apparatus generate heat and through convection heat the air. Variations in the temperature of the air within and in the immediate vicinity of the apparatus cause pressure differentials which in turn cause air flow. Similarly, the movement of the data card and the strobe generator within the narrow space provided for them in the apparatus creates air movement with corresponding pressure differentials and turbulence. Dust or dirt particles carried by either the air or the data card itself accumulate over time on the various internal parts of the apparatus including the light sources and the photoelectric cells. A sufficient accumulation of this foreign matter obliterates the light sending and light receiving devices. When this occurs, the affected punched holes in the data card are not detected by the card reader.
Due to the potential problem of dirt accumulation, optical punched card readers of this type require frequent cleaning to prevent malfunction. Obviously, this cleaning process imposes an additional cost upon the operation of the apparatus.
Accordingly, it is an object of the subject invention to provide an optical punched card reader that requires considerably less maintenance and cleaning.
It is another object of the subject invention to provide an optical punched card reader that is less susceptible of misreading the data instructions on the punched card.